The sight you are patterning from is made by Hard-Core Mfg. I have a set and they are fantastic. Rick has sold quite a few of those. The quality is absolutely top notch. http://www.hard-coremfg.com/index.htmI am borrowing the basic mounting design from an unknown maker that I found on the bmgparts.com sight.
If the set up you are referring to was for the MG42 spider quadrant, then it was an adapter/post set that I made some years back. Didn't make anymore since they were a bit too "Pricey" for the market at $75.00, but you might find a set used somewhere.Somebody was making an adapter for the spider sight I have.
The 1st peice mounted to the shroud and the sight went onto it
the 2nd peice was a sight post went on the rear sight of gun
Anyone know where I can get that shroud adapter?